Hi Marvin

I don't believe the XSF should maintain a registry of payment schemes
or systems or specific proof types for payment schemes. This is not our
field of expertise and this should be happening elsewhere. I understand
with RFC 8905 there is already some standard and a corresponding
registry and we could entirely rely on that (or any other open standard
with a suitable registry) instead of doing our own.

I've submitted a new revision on Github that removes the registry
for payment schemes, systems and proof formats.

A payment option is now a payment URI, and the payment system is
identified by that URI scheme.

The only registry that remains is the invoice-request service-context list
 (muc-entry, file-upload etc.), which is still XMPP application semantics.

I also would want to refrain to include any specific crypto-currency
network or technology in a specification document, because else there
will be a ton of stuff to specify: The industry site CoinMarketCap
lists more than 150 "Layer 1" crypto-currencies and "competition" in
the industry is largely about being mentioned in some "official"
sounding documents, so soon everyone will want to have a XEP if we open
that can of worms.

I agree on the substance and the new revision is now even more
generic because payment systems are purely identified by their
URI schemes. I've also generalized the prose in certain areas.

I did however keep a small number of illustrative examples. This
follows established XSF practice of naming concrete third-party
technologies as examples. For example XEP-0266 names specific
codecs (Opus, Speex, G.711), without pretending to be exhaustive.

There's also a very unhelpful part where you say that currency is ISO
4217 or non-ISO code. That makes it effectively "put anything here".
The part where the amount field also includes the currency code is also
weird to me (usually we would want to use our XML syntax instead of a
custom syntax), but that's a minor.

Fair. I've removed the "amount" attribute entirely in the latest revision.

The amount, currency and beneficiary are now carried inside the
payment URI and governed by that scheme's own standard and
we define no amount or currency syntax of our own.

I've kept "display-amount" to avoid clients having to be able to
parse payment URIs, but it's non-authoritative.

So my suggestion is to mostly piggy-back on top of RFC 8905 (or any
other suitable open standard specification) and have lighting or
whatever cryptocurrency network you want to support be integrated with
those people that actually do know payments much better than the XSF.

Marvin

On Fri, 2026-04-24 at 10:26 +0000, Daniel Gultsch wrote:

The XMPP Extensions Editor has received a proposal for a new XEP.

Title: Payment Required
Abstract:
This specification defines an XMPP protocol extension that enables
services to require payment before granting access to a resource. It
provides a payment-system neutral invoice format supporting multiple
concurrent payment options, including bank transfers (SEPA, IBAN,
UPI)
and instant-settlement networks (Lightning Network), and integrates
with the existing CAPTCHA challenge mechanism defined in XEP-0158.

URL: https://xmpp.org/extensions/inbox/payment-required.html

The Council will decide in the next two weeks whether to accept this
proposal as an official XEP.
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